Artificial lift systems, such as Electric Submersible Pump (ESP) systems, are often used in hydrocarbon producing wells to pump fluids from the well up to the surface. The downhole pump motor in an ESP system is typically driven by three-phase power carried from the surface on an armored cable. A number of existing systems further exploit the power-carrying conductors for data communications between downhole sensors and electronic control systems at the surface, enabling the control system to monitor the performance of the pump, to detect faults, and in many cases, to adjust the voltage and frequency of the three-phase power signal as needed to optimize operation of the artificial lift system. Factors for optimization may include safety, production rate, production cost, equipment life, and system reliability.
Each of the techniques employed by existing systems to communicate data on the power-carrying conductors are known to suffer from one or more of the following shortcomings. These shortcomings include: loss of communication when the motor is not running; loss of communication when one of the power-carrying conductors is grounded; inoperability due to drift in electrical component parameters; and requirements for an excessive number of high-voltage circuit components, resulting in reduced reliability. In fact, it is common for a sizeable fraction of ESP systems operating at any given time to be without downhole data communications due to one or more of these shortcomings.
It should be understood, however, that the specific embodiments given in the drawings and detailed description do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.